1. Field of the Invention
The invention is directed to an auditory canal insert for hearing aids of the type composed of a member introducible into the outer auditory canal with an acoustic channel to the tympanic membrane and having means for positioning the member in and sealing the member from the auditory canal. A seal ring of soft elastic material which fits against the walls of the auditory canal can be plugged into a retainer groove of the member and seals the annular gap between the outside contour of the member and the auditory canal in a sound-damping fashion. The invention is also directed to a seal and retainer element for in-the-ear hearing aids introducible into the auditory canal.
2. Description of the Prior Art
Otoplastics and customized ear adapters are especially employed when matching a hearing aid to the shape of the auditory canal of the ear of a hearing-impaired person. Such otoplastics and ear adapters function, first, for firmly positioning the hearing aid, so that the hearing aid cannot slip or fall out of the ear. Further, the otoplastic or ear adapter has a sound-damping effect in order to prevent feedback between the microphone and the earphone of the hearing aid. Otoplastics usually serve as an adapter for in-the-ear hearing aids (ItE aids), in contrast to ear adapters, which are suitable for behind-the-ear hearing aids (BtE aids).
In the standard manufacturing method of otoplastics and customized ear adapters, an impression of the auditory canal of the ear of the acoustically impaired person who is to wear the hearing aid is first made. Thereafter, a negative is shaped with the impression. Only then can an otoplastic or an ear adapter that is matched in shape to the auditory canal of the ear be produced therefrom. Frequently, the otoplastic or the ear adapter must still be trimmed or ground after manufacture in order to eliminate casting errors. Since this procedure is expensive and time-consuming, manufacturers have long attempted to develop a method with which the production of an impression and the production of a negative can be avoided.
For example, German AS 12 31 304 discloses a method wherein a self-hardening plastic is distributed on a base member that simulates the basic shape of the auditory canal of the human ear and the coated base member is subsequently inserted directly into the auditory canal of the hearing-impaired person until the plastic, which has now adapted to the inside counter of the auditory canal, has hardened. The matching to the inside contour, however, is not always optimum. As a result of pressing the basic form coated with plastic into the ear, there is the risk of pressing plastic too far into the auditory canal. In this method, moreover, a multitude of different, standard base members is required, since the plastic coating is insufficient for adequately adapting to shapes of auditory canal given employment of a uniform base member.
Formed parts of foamed material have been recently developed for ear adapters. Such formed parts of foamed material have been known for a long time as anti-noise plugs and are mass produced. A matching to individual auditory canals is not implemented. The parts of foamed material are merely compressed and plugged into the ear, where they subsequently expand to conform to the surrounding shape. 3M, is a manufacturer of such foam plugs (see, for example, the article "Disposable foam earmolds" by Smolak et al., in Hearing Instruments, volume 38, No. 12, 1987). Such foams, however, are less suited as a pure otoplastic replacement for an in-the-ear hearing aid since the foamed material is too soft. Moreover, such porous foamed materials are quickly contaminated by cerumen, etc., and must be replaced frequently. Such foams are also not optimum as ear adapters.
German Utility Model 1 779 936 discloses an ear adapter for connection to an earphone or to a sound conduit of a hearing aid. This adapter is shaped of a comparatively solid, malleable-elastic main member of plastic or rubber such that it presses against the walls of the auditory canal over its entire circumference in at least portions thereof. The main member is tapered at its end facing toward the inside of the ear and is provided with a retainer groove and following cone, whereby a seal ring that likewise presses against the walls of the auditory canal at its circumference and is composed of a softer, likewise malleable-elastic material is seated on the retainer groove and the cone. The main member and the seal ring are expediently plugged onto one another and can be easily separated from one another. Given this ear adapter as well as the similarly fashioned ear adapters of German Utility Models 79 29 224 and 79 29 226, standard base members of different sizes are required dependent on the size of the auditory canal and the wearing comfort is diminished because of the pressure of the adapter against the wall of the auditory canal.